I really like the cell shading work that you're doing here p6r. Are you able to adjust the line thickness and darkness to emphasize different parts of an image? I can't imagine how you'd be able to implement that type of logic since there's so much variation that just seems artistic in nature instead of rule based.

Here it's possible to change the thickness and the darkness of each "gradient" color, the number of gradient colors, the contrast (more or less) between the colors, to have more or less light, to modify the orientation of the light and shadow, to add outlines or not, to add some texture or not.

You can see the differences here between this picture and the one above.

Oh wow, the last one is really cool! By "emphasize" I mean to call attention too. I'm thinking in terms of making the line art thicker and/or darker to emphasize. While the un-emphasized line is thinner and/or lighter.